Driver coaching systems may convey feedback or fuel efficiency rating to drivers based on smoothness of acceleration, smoothness of braking and average vehicle speed. The systems typically calculate the rating without regard to posted speed limits, other road signs, traffic congestion or other environmental conditions. In one example, a vehicle may reach its highest fuel economy when the vehicle is operated at an optimum fuel efficient speed of approximately 55 kilometers per hour (35 miles per hour). This vehicle may not be operated at the optimum speed when, for example, the vehicle travels on a freeway having a minimum speed limit of about 70 kph (45 mph), and the coaching system for this vehicle may not adequately credit or may even decrease the fuel efficiency rating because the actual vehicle speed is traveling substantially faster than the optimum speed. Similarly, the same coaching system may decrease the fuel efficiency rating when the vehicle is traveling in a residential area having a maximum speed limit of 40 kph (25 mph) and the driver is abiding by the posted maximum speed limit well below the optimum speed. In this respect, existing coaching systems may penalize or not adequately credit a driver who complies with local traffic laws.
On the other hand, the system may also unduly credit or increase the fuel efficiency rating when the average vehicle speed is at or near an optimum speed due to frequent stop-and-go driving. Continuing with the previous example of the vehicle having an optimum speed of 55 kph (35 mph), the vehicle may travel along an inner city road at an average speed substantially close to the optimum speed, as a result of the vehicle idling at a full stop at multiple traffic lights and accelerating up to a top speed of at least 70 kph (45 mph) between traffic lights without ever maintaining a cruising speed of 55 kph (35 mph). In this respect, the system may provide an unduly high fuel efficiency rating despite the generally excessive vehicle speed above the optimum fuel efficient speed and idling at full stops.
A need exists to coach a driver to operate his vehicle in a manner that improves the fuel economy of the car, without encouraging the driver to violate traffic laws or disregard other road conditions.